Various imaging techniques are currently in use to diagnose, stage, and monitor various diseases, such as neurological disorders and tumors. Each technique currently in use has certain drawbacks. For example, epileptic regions of activity in the brain are currently localized using electric (electroencephalogram (EEG), electrocorticogram (ECoG), and depth electrode implants), magnetic (magnetoencephalogram (MEG)), and radioactive techniques (positron emission tomography (PET), single photon emission computed tomography (SPECT). EEG and MEG are less sensitive to sources that are more than a few centimeters below the scalp surface and have less sensitivity for detecting epileptic sources of activity that are deeper in the brain parenchyma. The presence of multiple simultaneous sources further confounds quantitative localization due to degeneracy of mathematical solution. In addition, these methods rely on presence of ictal or interictal activity, which may not be present at the time of the testing. ECoG, and depth-implanted electrodes are invasive surgical techniques of considerable cost and health risk, and cause discomfort in patients.
As another example, many primary or metastatic neoplasms cannot be differentiated from normal tissues. PET, PET-computed tomography (PET-CT), and SPECT are used routinely to look for tumor activity so as to grade tumors. PET and SPECT involve administration of radioactive substances. PET traces have short half-life times, are not widely available, and are limited in their usefulness as diagnostic techniques.
There is a need in the art for diagnostic tracers and methods that avoid one or more of the above-mentioned drawbacks.
Literature
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